Alex Cohen is on a date - sort of. He's having Thai food in the Castro with his new friend Sean, whom he met through his iPhone, all the while texting nine other guys whom he might hook up with later.

Not that Sean is offended. Between bites of fried calamari, he's texting a handful of other men who might become his Mr. Right for the night.

They are "grinding," the latest verb in the gay lexicon, which refers to the new gay dating app for the iPhone called Grindr. A revolutionary way to meet gay men, Grindr has eliminated the need for "gay-dar"; it uses GPS technology to download hundreds of pictures of available men within walking distance.

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Alex and Sean can click on a man's picture to start a text conversation, send pictures and, if they so desire, make arrangements for a rendezvous. There's a number on each man's photo, indicating how many feet away they are at that instant.

"It's so much better than Web sites like Manhunt.net, where you have to send e-mails and wait for a response," said Sean, 44. "It's not like picking up men was difficult before, but this has changed it so that you don't have to do any work whatsoever."

No more need for a pickup line. No more accidentally hitting on straight guys. No more wondering whether the object of your desire is desirous of you. Goodbye, awkward two-hour date.

"I'd always be sitting in rooms and wonder, 'Is that guy gay?' And now you can find out in a more comfortable, modern way," said 33-year-old Joel Simkhai of Los Angeles, a former online marketer who created Grindr in spring 2009.

As of this month, Grindr has 500,000 users worldwide, Simkhai says, and 2,000 more join daily. The 20,000 Bay Area users make San Francisco one of Grindr's busiest hubs, behind New York, Los Angeles and London.

Simkhai has heard reports of men using Grindr in Iran, Israel, Kazakhstan and on the same Virgin America flight with Wi-Fi.

Blocking creeps

There's even an offshoot blog, Guys I Blocked on Grindr, where people post Grindr profile pictures of men who creeped them out for one reason or another - including one man who posed on Grindr with a gun.

Creators have used the Grindr network to mobilize users for rallies supporting same-sex marriage, and for charity events that support gay causes.

Singer Lady Gaga is rumored to have crashed a Grindr party in Los Angeles that was advertised through the app's network.

"There's a lot of opportunity to use Grindr as a tool to connect the gay community and make it stronger," Simkhai said.

The free version of the app is supported by ads, and the $2.99 monthly ad-free version allows users to view twice the number of men - 200 - at once. It also has an e-mail notification feature, which heavy Grindr users like because it saves the iPhone battery.

"Like any dating site or Craigslist, you have to be smart, and only reveal what you feel safe sharing," he said.

A straight version of Grindr is in the works, and Simkhai has a survey for lesbians on Grindr.com to see whether they want one of their own. Soon Grindr will work on a BlackBerry, he said.

During a five-week trip to Australia, 45-year-old Jeff Ford of San Francisco used Grindr to make friends who took him to the beach and to a rooftop party.

Wayne Carlson, 58, who is in a committed relationship, uses Grindr to strike up conversations with like-minded men in Minnesota about hockey, new bars that are opening, what's going on in the gay-marriage debate.

"I know there's a pickup aspect to Grindr, but I think for most of the young men on there, they use it differently than guys like me," he said.

Carlson was at a beer garden at the Minnesota State Fair when he discovered that the man at the other end of the bar was on Grindr.

"I like to use it to find out who is in my neighborhood. ... I kinda equate it to being Polish and finding all the other Polish people around you - it's like a community thing," he said.

Doubling up

Alex and Sean use it every day to chat and plan dates. Sometimes they invite men to go on dates with both of them.

During dinner, Sean got a hello message from 30-year-old Octavio, wearing only a towel, with star tattoos on his arm. According to Grindr, he was 148 feet away.

"Hot pic!" Sean texted back.

"I at least talk to anyone who messages me," said Cohen, 22, who moved to Berkeley recently for college and used Grindr to find all his new friends.

"But then I have my stable - I have like six that I've become closer with, like Sean, who I see on a more regular basis," he said.

Some of the men they chatted with during dinner just wanted to say hi, others wanted to talk dirty and skip the small chat.

While Apple restricts what users put on their profiles - no nudity and no profanity - there's no censorship of private texts between two people.

Sometimes men who are considering getting together share photos of themselves in various states of undress, Cohen said.

"It can seem crass sometimes, but it's also a way to quickly find out if the person likes to do the same kinds of things you do without having to ask them outright in public," Sean said.

Hard to focus

The immediacy is what's great, and not-so-great, about Grindr, said 33-year-old Jayson Jaynes of San Francisco. Faced with so many options, it's easy to dismiss, and hard to focus on, any one person.

"Grindr is like ordering Chinese food that you can send back if you don't like it because it's free," Jaynes said. "But on the flip side, it's becoming so easy that people aren't having real conversations anymore - it's like they don't really care about one another."

During dinner, Alex and Sean invited a few Grindr buddies to meet them at their next stop, the bar 440 Castro.

Inside was standing room only, and a go-go boy was dancing above the crowd in bikini briefs. Alex and Sean checked their iPhones to see who was grinding, and within minutes they spotted Joe Armenia, who looked up from his iPhone and smiled and waved them over.

The three men talked for a little bit, then Cohen and Sean left for another bar, where the fashion design reality series "Project Runway" was showing on the big screen.

The night was still young. And their iPhone batteries were still strong.

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